avconv: rewrite -qscale and -aq handling.

[coroid/ffmpeg_saccubus.git] / doc / avconv.texi

\input texinfo @c -*- texinfo -*-

@settitle avconv Documentation
@titlepage
@center @titlefont{avconv Documentation}
@end titlepage

@top

@contents

@chapter Synopsis

The generic syntax is:

@example
@c man begin SYNOPSIS
avconv [[infile options][@option{-i} @var{infile}]]... @{[outfile options] @var{outfile}@}...
@c man end
@end example

@chapter Description
@c man begin DESCRIPTION

avconv is a very fast video and audio converter that can also grab from
a live audio/video source. It can also convert between arbitrary sample
rates and resize video on the fly with a high quality polyphase filter.

The command line interface is designed to be intuitive, in the sense
that avconv tries to figure out all parameters that can possibly be
derived automatically. You usually only have to specify the target
bitrate you want.

As a general rule, options are applied to the next specified
file. Therefore, order is important, and you can have the same
option on the command line multiple times. Each occurrence is
then applied to the next input or output file.

@itemize
@item
To set the video bitrate of the output file to 64kbit/s:
@example
avconv -i input.avi -b 64k output.avi
@end example

@item
To force the frame rate of the output file to 24 fps:
@example
avconv -i input.avi -r 24 output.avi
@end example

@item
To force the frame rate of the input file (valid for raw formats only)
to 1 fps and the frame rate of the output file to 24 fps:
@example
avconv -r 1 -i input.m2v -r 24 output.avi
@end example
@end itemize

The format option may be needed for raw input files.

By default avconv tries to convert as losslessly as possible: It
uses the same audio and video parameters for the outputs as the one
specified for the inputs.

@c man end DESCRIPTION

@chapter Stream selection
@c man begin STREAM SELECTION

By default avconv tries to pick the "best" stream of each type present in input
files and add them to each output file. For video, this means the highest
resolution, for audio the highest channel count. For subtitle it's simply the
first subtitle stream.

You can disable some of those defaults by using @code{-vn/-an/-sn} options. For
full manual control, use the @code{-map} option, which disables the defaults just
described.

@c man end STREAM SELECTION

@chapter Options
@c man begin OPTIONS

@include fftools-common-opts.texi

@section Main options

@table @option

@item -f @var{fmt}
Force format.

@item -i @var{filename}
input file name

@item -y
Overwrite output files.

@item -c[:@var{stream_type}][:@var{stream_index}] @var{codec}
@item -codec[:@var{stream_type}][:@var{stream_index}] @var{codec}
Select an encoder (when used before an output file) or a decoder (when used
before an input file) for one or more streams. @var{codec} is the name of a
decoder/encoder or a special value @code{copy} (output only) to indicate that
the stream is not to be reencoded.

@var{stream_type} may be 'v' for video, 'a' for audio, 's' for subtitle and 'd'
for data streams.  @var{stream_index} is a global zero-based stream index if
@var{stream_type} isn't given, otherwise it counts only streams of the given
type. If @var{stream_index} is omitted, this option applies to all streams of
the given type or all streams of any type if @var{stream_type} is missing as
well (note that this only makes sense when all streams are of the same type or
@var{codec} is @code{copy}).

For example
@example
avconv -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT
@end example
encodes all video streams with libx264 and copies all audio streams.

For each stream, the last matching @code{c} option is applied, so
@example
avconv -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT
@end example
will copy all the streams except the second video, which will be encoded with
libx264, and the 138th audio, which will be encoded with libvorbis.

@item -t @var{duration}
Restrict the transcoded/captured video sequence
to the duration specified in seconds.
@code{hh:mm:ss[.xxx]} syntax is also supported.

@item -fs @var{limit_size}
Set the file size limit.

@item -ss @var{position}
When used as an input option (before @code{-i}), seeks in this input file to
@var{position}. When used as an output option (before an output filename),
decodes but discards input until the timestamps reach @var{position}. This is
slower, but more accurate.

@var{position} may be either in seconds or in @code{hh:mm:ss[.xxx]} form.

@item -itsoffset @var{offset}
Set the input time offset in seconds.
@code{[-]hh:mm:ss[.xxx]} syntax is also supported.
The offset is added to the timestamps of the input files.
Specifying a positive offset means that the corresponding
streams are delayed by 'offset' seconds.

@item -timestamp @var{time}
Set the recording timestamp in the container.
The syntax for @var{time} is:
@example
now|([(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH[:MM[:SS[.m...]]])|(HH[MM[SS[.m...]]]))[Z|z])
@end example
If the value is "now" it takes the current time.
Time is local time unless 'Z' or 'z' is appended, in which case it is
interpreted as UTC.
If the year-month-day part is not specified it takes the current
year-month-day.

@item -metadata[:metadata_specifier] @var{key}=@var{value}
Set a metadata key/value pair.

An optional @var{metadata_specifier} may be given to set metadata
on streams or chapters. See @code{-map_metadata} documentation for
details.

This option overrides metadata set with @code{-map_metadata}. It is
also possible to delete metadata by using an empty value.

For example, for setting the title in the output file:
@example
avconv -i in.avi -metadata title="my title" out.flv
@end example

To set the language of the second stream:
@example
avconv -i INPUT -metadata:s:1 language=eng OUTPUT
@end example

@item -v @var{number}
Set the logging verbosity level.

@item -target @var{type}
Specify target file type ("vcd", "svcd", "dvd", "dv", "dv50", "pal-vcd",
"ntsc-svcd", ... ). All the format options (bitrate, codecs,
buffer sizes) are then set automatically. You can just type:

@example
avconv -i myfile.avi -target vcd /tmp/vcd.mpg
@end example

Nevertheless you can specify additional options as long as you know
they do not conflict with the standard, as in:

@example
avconv -i myfile.avi -target vcd -bf 2 /tmp/vcd.mpg
@end example

@item -dframes @var{number}
Set the number of data frames to record. This is an alias for @code{-frames:d}.

@item -frames[:stream_specifier] @var{framecount}
Stop writing to the stream after @var{framecount} frames.

@item -q @var{q}
@item -qscale @var{q}
Use fixed quality scale (VBR). The meaning of @var{q} is
codec-dependent.

@end table

@section Video Options

@table @option
@item -vframes @var{number}
Set the number of video frames to record. This is an alias for @code{-frames:v}.
@item -r @var{fps}
Set frame rate (Hz value, fraction or abbreviation), (default = 25).
@item -s @var{size}
Set frame size. The format is @samp{wxh} (avserver default = 160x128, avconv default = same as source).
The following abbreviations are recognized:
@table @samp
@item sqcif
128x96
@item qcif
176x144
@item cif
352x288
@item 4cif
704x576
@item 16cif
1408x1152
@item qqvga
160x120
@item qvga
320x240
@item vga
640x480
@item svga
800x600
@item xga
1024x768
@item uxga
1600x1200
@item qxga
2048x1536
@item sxga
1280x1024
@item qsxga
2560x2048
@item hsxga
5120x4096
@item wvga
852x480
@item wxga
1366x768
@item wsxga
1600x1024
@item wuxga
1920x1200
@item woxga
2560x1600
@item wqsxga
3200x2048
@item wquxga
3840x2400
@item whsxga
6400x4096
@item whuxga
7680x4800
@item cga
320x200
@item ega
640x350
@item hd480
852x480
@item hd720
1280x720
@item hd1080
1920x1080
@end table

@item -aspect @var{aspect}
Set the video display aspect ratio specified by @var{aspect}.

@var{aspect} can be a floating point number string, or a string of the
form @var{num}:@var{den}, where @var{num} and @var{den} are the
numerator and denominator of the aspect ratio. For example "4:3",
"16:9", "1.3333", and "1.7777" are valid argument values.

@item -vn
Disable video recording.
@item -bt @var{tolerance}
Set video bitrate tolerance (in bits, default 4000k).
Has a minimum value of: (target_bitrate/target_framerate).
In 1-pass mode, bitrate tolerance specifies how far ratecontrol is
willing to deviate from the target average bitrate value. This is
not related to min/max bitrate. Lowering tolerance too much has
an adverse effect on quality.
@item -maxrate @var{bitrate}
Set max video bitrate (in bit/s).
Requires -bufsize to be set.
@item -minrate @var{bitrate}
Set min video bitrate (in bit/s).
Most useful in setting up a CBR encode:
@example
avconv -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v
@end example
It is of little use elsewise.
@item -bufsize @var{size}
Set video buffer verifier buffer size (in bits).
@item -vcodec @var{codec}
Set the video codec. This is an alias for @code{-codec:v}.
@item -same_quant
Use same quantizer as source (implies VBR).

Note that this is NOT SAME QUALITY. Do not use this option unless you know you
need it.

@item -pass @var{n}
Select the pass number (1 or 2). It is used to do two-pass
video encoding. The statistics of the video are recorded in the first
pass into a log file (see also the option -passlogfile),
and in the second pass that log file is used to generate the video
at the exact requested bitrate.
On pass 1, you may just deactivate audio and set output to null,
examples for Windows and Unix:
@example
avconv -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y NUL
avconv -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y /dev/null
@end example

@item -passlogfile @var{prefix}
Set two-pass log file name prefix to @var{prefix}, the default file name
prefix is ``av2pass''. The complete file name will be
@file{PREFIX-N.log}, where N is a number specific to the output
stream.

@item -vf @var{filter_graph}
@var{filter_graph} is a description of the filter graph to apply to
the input video.
Use the option "-filters" to show all the available filters (including
also sources and sinks).

@end table

@section Advanced Video Options

@table @option
@item -pix_fmt @var{format}
Set pixel format. Use 'list' as parameter to show all the supported
pixel formats.
@item -sws_flags @var{flags}
Set SwScaler flags.
@item -g @var{gop_size}
Set the group of pictures size.
@item -vdt @var{n}
Discard threshold.
@item -qmin @var{q}
minimum video quantizer scale (VBR)
@item -qmax @var{q}
maximum video quantizer scale (VBR)
@item -qdiff @var{q}
maximum difference between the quantizer scales (VBR)
@item -qblur @var{blur}
video quantizer scale blur (VBR) (range 0.0 - 1.0)
@item -qcomp @var{compression}
video quantizer scale compression (VBR) (default 0.5).
Constant of ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0

@item -lmin @var{lambda}
minimum video lagrange factor (VBR)
@item -lmax @var{lambda}
max video lagrange factor (VBR)
@item -mblmin @var{lambda}
minimum macroblock quantizer scale (VBR)
@item -mblmax @var{lambda}
maximum macroblock quantizer scale (VBR)

These four options (lmin, lmax, mblmin, mblmax) use 'lambda' units,
but you may use the QP2LAMBDA constant to easily convert from 'q' units:
@example
avconv -i src.ext -lmax 21*QP2LAMBDA dst.ext
@end example

@item -rc_init_cplx @var{complexity}
initial complexity for single pass encoding
@item -b_qfactor @var{factor}
qp factor between P- and B-frames
@item -i_qfactor @var{factor}
qp factor between P- and I-frames
@item -b_qoffset @var{offset}
qp offset between P- and B-frames
@item -i_qoffset @var{offset}
qp offset between P- and I-frames
@item -rc_eq @var{equation}
Set rate control equation (see section "Expression Evaluation")
(default = @code{tex^qComp}).

When computing the rate control equation expression, besides the
standard functions defined in the section "Expression Evaluation", the
following functions are available:
@table @var
@item bits2qp(bits)
@item qp2bits(qp)
@end table

and the following constants are available:
@table @var
@item iTex
@item pTex
@item tex
@item mv
@item fCode
@item iCount
@item mcVar
@item var
@item isI
@item isP
@item isB
@item avgQP
@item qComp
@item avgIITex
@item avgPITex
@item avgPPTex
@item avgBPTex
@item avgTex
@end table

@item -rc_override @var{override}
rate control override for specific intervals
@item -me_method @var{method}
Set motion estimation method to @var{method}.
Available methods are (from lowest to best quality):
@table @samp
@item zero
Try just the (0, 0) vector.
@item phods
@item log
@item x1
@item hex
@item umh
@item epzs
(default method)
@item full
exhaustive search (slow and marginally better than epzs)
@end table

@item -dct_algo @var{algo}
Set DCT algorithm to @var{algo}. Available values are:
@table @samp
@item 0
FF_DCT_AUTO (default)
@item 1
FF_DCT_FASTINT
@item 2
FF_DCT_INT
@item 3
FF_DCT_MMX
@item 4
FF_DCT_MLIB
@item 5
FF_DCT_ALTIVEC
@end table

@item -idct_algo @var{algo}
Set IDCT algorithm to @var{algo}. Available values are:
@table @samp
@item 0
FF_IDCT_AUTO (default)
@item 1
FF_IDCT_INT
@item 2
FF_IDCT_SIMPLE
@item 3
FF_IDCT_SIMPLEMMX
@item 4
FF_IDCT_LIBMPEG2MMX
@item 5
FF_IDCT_PS2
@item 6
FF_IDCT_MLIB
@item 7
FF_IDCT_ARM
@item 8
FF_IDCT_ALTIVEC
@item 9
FF_IDCT_SH4
@item 10
FF_IDCT_SIMPLEARM
@end table

@item -er @var{n}
Set error resilience to @var{n}.
@table @samp
@item 1
FF_ER_CAREFUL (default)
@item 2
FF_ER_COMPLIANT
@item 3
FF_ER_AGGRESSIVE
@item 4
FF_ER_VERY_AGGRESSIVE
@end table

@item -ec @var{bit_mask}
Set error concealment to @var{bit_mask}. @var{bit_mask} is a bit mask of
the following values:
@table @samp
@item 1
FF_EC_GUESS_MVS (default = enabled)
@item 2
FF_EC_DEBLOCK (default = enabled)
@end table

@item -bf @var{frames}
Use 'frames' B-frames (supported for MPEG-1, MPEG-2 and MPEG-4).
@item -mbd @var{mode}
macroblock decision
@table @samp
@item 0
FF_MB_DECISION_SIMPLE: Use mb_cmp (cannot change it yet in avconv).
@item 1
FF_MB_DECISION_BITS: Choose the one which needs the fewest bits.
@item 2
FF_MB_DECISION_RD: rate distortion
@end table

@item -4mv
Use four motion vector by macroblock (MPEG-4 only).
@item -part
Use data partitioning (MPEG-4 only).
@item -bug @var{param}
Work around encoder bugs that are not auto-detected.
@item -strict @var{strictness}
How strictly to follow the standards.
@item -aic
Enable Advanced intra coding (h263+).
@item -umv
Enable Unlimited Motion Vector (h263+)

@item -deinterlace
Deinterlace pictures.
@item -ilme
Force interlacing support in encoder (MPEG-2 and MPEG-4 only).
Use this option if your input file is interlaced and you want
to keep the interlaced format for minimum losses.
The alternative is to deinterlace the input stream with
@option{-deinterlace}, but deinterlacing introduces losses.
@item -psnr
Calculate PSNR of compressed frames.
@item -vstats
Dump video coding statistics to @file{vstats_HHMMSS.log}.
@item -vstats_file @var{file}
Dump video coding statistics to @var{file}.
@item -top @var{n}
top=1/bottom=0/auto=-1 field first
@item -dc @var{precision}
Intra_dc_precision.
@item -vtag @var{fourcc/tag}
Force video tag/fourcc. This is an alias for @code{-tag:v}.
@item -qphist
Show QP histogram.
@item -force_key_frames @var{time}[,@var{time}...]
Force key frames at the specified timestamps, more precisely at the first
frames after each specified time.
This option can be useful to ensure that a seek point is present at a
chapter mark or any other designated place in the output file.
The timestamps must be specified in ascending order.
@end table

@section Audio Options

@table @option
@item -aframes @var{number}
Set the number of audio frames to record. This is an alias for @code{-frames:a}.
@item -ar @var{freq}
Set the audio sampling frequency. For output streams it is set by
default to the frequency of the corresponding input stream. For input
streams this option only makes sense for audio grabbing devices and raw
demuxers and is mapped to the corresponding demuxer options.
@item -aq @var{q}
Set the audio quality (codec-specific, VBR). This is an alias for -q:a.
@item -ac @var{channels}
Set the number of audio channels. For output streams it is set by
default to the number of input audio channels. For input streams
this option only makes sense for audio grabbing devices and raw demuxers
and is mapped to the corresponding demuxer options.
@item -an
Disable audio recording.
@item -acodec @var{codec}
Set the audio codec. This is an alias for @code{-codec:a}.
@item -sample_fmt[:@var{stream_specifier}] @var{sample_fmt}
Set the audio sample format. Use @code{-help sample_fmts} to get a list
of supported sample formats.
@end table

@section Advanced Audio options:

@table @option
@item -atag @var{fourcc/tag}
Force audio tag/fourcc. This is an alias for @code{-tag:a}.
@item -audio_service_type @var{type}
Set the type of service that the audio stream contains.
@table @option
@item ma
Main Audio Service (default)
@item ef
Effects
@item vi
Visually Impaired
@item hi
Hearing Impaired
@item di
Dialogue
@item co
Commentary
@item em
Emergency
@item vo
Voice Over
@item ka
Karaoke
@end table
@end table

@section Subtitle options:

@table @option
@item -scodec @var{codec}
Set the subtitle codec. This is an alias for @code{-codec:s}.
@item -sn
Disable subtitle recording.
@end table

@section Audio/Video grab options

@table @option
@item -isync
Synchronize read on input.
@end table

@section Advanced options

@table @option
@item -map [-]@var{input_file_id}[:@var{input_stream_type}][:@var{input_stream_id}][,@var{sync_file_id}[:@var{sync_stream_type}][:@var{sync_stream_id}]]

Designate one or more input streams as a source for the output file. Each input
stream is identified by the input file index @var{input_file_id} and
the input stream index @var{input_stream_id} within the input
file. Both indices start at 0. If specified,
@var{sync_file_id}:@var{sync_stream_id} sets which input stream
is used as a presentation sync reference.

If @var{input_stream_type} is specified -- 'v' for video, 'a' for audio, 's' for
subtitle and 'd' for data -- then @var{input_stream_id} counts only the streams
of this type. Same for @var{sync_stream_type}.

@var{input_stream_id} may be omitted, in which case all streams of the given
type are mapped (or all streams in the file, if no type is specified).

The first @code{-map} option on the command line specifies the
source for output stream 0, the second @code{-map} option specifies
the source for output stream 1, etc.

A @code{-} character before the stream identifier creates a "negative" mapping.
It disables matching streams from already created mappings.

For example, to map ALL streams from the first input file to output
@example
avconv -i INPUT -map 0 output
@end example

For example, if you have two audio streams in the first input file,
these streams are identified by "0:0" and "0:1". You can use
@code{-map} to select which streams to place in an output file. For
example:
@example
avconv -i INPUT -map 0:1 out.wav
@end example
will map the input stream in @file{INPUT} identified by "0:1" to
the (single) output stream in @file{out.wav}.

For example, to select the stream with index 2 from input file
@file{a.mov} (specified by the identifier "0:2"), and stream with
index 6 from input @file{b.mov} (specified by the identifier "1:6"),
and copy them to the output file @file{out.mov}:
@example
avconv -i a.mov -i b.mov -c copy -map 0:2 -map 1:6 out.mov
@end example

To select all video and the third audio stream from an input file:
@example
avconv -i INPUT -map 0:v -map 0:a:2 OUTPUT
@end example

To map all the streams except the second audio, use negative mappings
@example
avconv -i INPUT -map 0 -map -0:a:1 OUTPUT
@end example

Note that using this option disables the default mappings for this output file.

@item -map_metadata[:@var{metadata_type}][:@var{index}] @var{infile}[:@var{metadata_type}][:@var{index}]
Set metadata information of the next output file from @var{infile}. Note that
those are file indices (zero-based), not filenames.
Optional @var{metadata_type} parameters specify, which metadata to copy - (g)lobal
(i.e. metadata that applies to the whole file), per-(s)tream, per-(c)hapter or
per-(p)rogram. All metadata specifiers other than global must be followed by the
stream/chapter/program index. If metadata specifier is omitted, it defaults to
global.

By default, global metadata is copied from the first input file,
per-stream and per-chapter metadata is copied along with streams/chapters. These
default mappings are disabled by creating any mapping of the relevant type. A negative
file index can be used to create a dummy mapping that just disables automatic copying.

For example to copy metadata from the first stream of the input file to global metadata
of the output file:
@example
avconv -i in.ogg -map_metadata 0:s:0 out.mp3
@end example
@item -map_chapters @var{input_file_index}
Copy chapters from input file with index @var{input_file_index} to the next
output file. If no chapter mapping is specified, then chapters are copied from
the first input file with at least one chapter. Use a negative file index to
disable any chapter copying.
@item -debug
Print specific debug info.
@item -benchmark
Show benchmarking information at the end of an encode.
Shows CPU time used and maximum memory consumption.
Maximum memory consumption is not supported on all systems,
it will usually display as 0 if not supported.
@item -dump
Dump each input packet.
@item -hex
When dumping packets, also dump the payload.
@item -bitexact
Only use bit exact algorithms (for codec testing).
@item -ps @var{size}
Set RTP payload size in bytes.
@item -re
Read input at native frame rate. Mainly used to simulate a grab device.
@item -threads @var{count}
Thread count.
@item -vsync @var{parameter}
Video sync method.

@table @option
@item 0
Each frame is passed with its timestamp from the demuxer to the muxer.
@item 1
Frames will be duplicated and dropped to achieve exactly the requested
constant framerate.
@item 2
Frames are passed through with their timestamp or dropped so as to
prevent 2 frames from having the same timestamp.
@item -1
Chooses between 1 and 2 depending on muxer capabilities. This is the
default method.
@end table

With -map you can select from which stream the timestamps should be
taken. You can leave either video or audio unchanged and sync the
remaining stream(s) to the unchanged one.

@item -async @var{samples_per_second}
Audio sync method. "Stretches/squeezes" the audio stream to match the timestamps,
the parameter is the maximum samples per second by which the audio is changed.
-async 1 is a special case where only the start of the audio stream is corrected
without any later correction.
@item -copyts
Copy timestamps from input to output.
@item -copytb
Copy input stream time base from input to output when stream copying.
@item -shortest
Finish encoding when the shortest input stream ends.
@item -dts_delta_threshold
Timestamp discontinuity delta threshold.
@item -muxdelay @var{seconds}
Set the maximum demux-decode delay.
@item -muxpreload @var{seconds}
Set the initial demux-decode delay.
@item -streamid @var{output-stream-index}:@var{new-value}
Assign a new stream-id value to an output stream. This option should be
specified prior to the output filename to which it applies.
For the situation where multiple output files exist, a streamid
may be reassigned to a different value.

For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for
an output mpegts file:
@example
avconv -i infile -streamid 0:33 -streamid 1:36 out.ts
@end example

@item -bsf[:@var{stream_specifier}] @var{bitstream_filters}
Set bitstream filters for matching streams. @var{bistream_filters} is
a comma-separated list of bitstream filters. Use the @code{-bsfs} option
to get the list of bitstream filters.
@example
avconv -i h264.mp4 -c:v copy -vbsf h264_mp4toannexb -an out.h264
@end example
@example
avconv -i file.mov -an -vn -sbsf mov2textsub -c:s copy -f rawvideo sub.txt
@end example

@item -tag[:@var{stream_specifier}] @var{codec_tag}
Force a tag/fourcc for matching streams.
@end table
@c man end OPTIONS

@chapter Tips
@c man begin TIPS

@itemize
@item
For streaming at very low bitrate application, use a low frame rate
and a small GOP size. This is especially true for RealVideo where
the Linux player does not seem to be very fast, so it can miss
frames. An example is:

@example
avconv -g 3 -r 3 -t 10 -b 50k -s qcif -f rv10 /tmp/b.rm
@end example

@item
The parameter 'q' which is displayed while encoding is the current
quantizer. The value 1 indicates that a very good quality could
be achieved. The value 31 indicates the worst quality. If q=31 appears
too often, it means that the encoder cannot compress enough to meet
your bitrate. You must either increase the bitrate, decrease the
frame rate or decrease the frame size.

@item
If your computer is not fast enough, you can speed up the
compression at the expense of the compression ratio. You can use
'-me zero' to speed up motion estimation, and '-intra' to disable
motion estimation completely (you have only I-frames, which means it
is about as good as JPEG compression).

@item
To have very low audio bitrates, reduce the sampling frequency
(down to 22050 Hz for MPEG audio, 22050 or 11025 for AC-3).

@item
To have a constant quality (but a variable bitrate), use the option
'-qscale n' when 'n' is between 1 (excellent quality) and 31 (worst
quality).

@end itemize
@c man end TIPS

@chapter Examples
@c man begin EXAMPLES

@section Video and Audio grabbing

If you specify the input format and device then avconv can grab video
and audio directly.

@example
avconv -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg
@end example

Note that you must activate the right video source and channel before
launching avconv with any TV viewer such as
@uref{http://linux.bytesex.org/xawtv/, xawtv} by Gerd Knorr. You also
have to set the audio recording levels correctly with a
standard mixer.

@section X11 grabbing

Grab the X11 display with avconv via

@example
avconv -f x11grab -s cif -r 25 -i :0.0 /tmp/out.mpg
@end example

0.0 is display.screen number of your X11 server, same as
the DISPLAY environment variable.

@example
avconv -f x11grab -s cif -r 25 -i :0.0+10,20 /tmp/out.mpg
@end example

0.0 is display.screen number of your X11 server, same as the DISPLAY environment
variable. 10 is the x-offset and 20 the y-offset for the grabbing.

@section Video and Audio file format conversion

Any supported file format and protocol can serve as input to avconv:

Examples:
@itemize
@item
You can use YUV files as input:

@example
avconv -i /tmp/test%d.Y /tmp/out.mpg
@end example

It will use the files:
@example
/tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
/tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
@end example

The Y files use twice the resolution of the U and V files. They are
raw files, without header. They can be generated by all decent video
decoders. You must specify the size of the image with the @option{-s} option
if avconv cannot guess it.

@item
You can input from a raw YUV420P file:

@example
avconv -i /tmp/test.yuv /tmp/out.avi
@end example

test.yuv is a file containing raw YUV planar data. Each frame is composed
of the Y plane followed by the U and V planes at half vertical and
horizontal resolution.

@item
You can output to a raw YUV420P file:

@example
avconv -i mydivx.avi hugefile.yuv
@end example

@item
You can set several input files and output files:

@example
avconv -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
@end example

Converts the audio file a.wav and the raw YUV video file a.yuv
to MPEG file a.mpg.

@item
You can also do audio and video conversions at the same time:

@example
avconv -i /tmp/a.wav -ar 22050 /tmp/a.mp2
@end example

Converts a.wav to MPEG audio at 22050 Hz sample rate.

@item
You can encode to several formats at the same time and define a
mapping from input stream to output streams:

@example
avconv -i /tmp/a.wav -map 0:a -b 64k /tmp/a.mp2 -map 0:a -b 128k /tmp/b.mp2
@end example

Converts a.wav to a.mp2 at 64 kbits and to b.mp2 at 128 kbits. '-map
file:index' specifies which input stream is used for each output
stream, in the order of the definition of output streams.

@item
You can transcode decrypted VOBs:

@example
avconv -i snatch_1.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a libmp3lame -b:a 128k snatch.avi
@end example

This is a typical DVD ripping example; the input is a VOB file, the
output an AVI file with MPEG-4 video and MP3 audio. Note that in this
command we use B-frames so the MPEG-4 stream is DivX5 compatible, and
GOP size is 300 which means one intra frame every 10 seconds for 29.97fps
input video. Furthermore, the audio stream is MP3-encoded so you need
to enable LAME support by passing @code{--enable-libmp3lame} to configure.
The mapping is particularly useful for DVD transcoding
to get the desired audio language.

NOTE: To see the supported input formats, use @code{avconv -formats}.

@item
You can extract images from a video, or create a video from many images:

For extracting images from a video:
@example
avconv -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg
@end example

This will extract one video frame per second from the video and will
output them in files named @file{foo-001.jpeg}, @file{foo-002.jpeg},
etc. Images will be rescaled to fit the new WxH values.

If you want to extract just a limited number of frames, you can use the
above command in combination with the -vframes or -t option, or in
combination with -ss to start extracting from a certain point in time.

For creating a video from many images:
@example
avconv -f image2 -i foo-%03d.jpeg -r 12 -s WxH foo.avi
@end example

The syntax @code{foo-%03d.jpeg} specifies to use a decimal number
composed of three digits padded with zeroes to express the sequence
number. It is the same syntax supported by the C printf function, but
only formats accepting a normal integer are suitable.

@item
You can put many streams of the same type in the output:

@example
avconv -i test1.avi -i test2.avi -map 0.3 -map 0.2 -map 0.1 -map 0.0 -c copy test12.nut
@end example

The resulting output file @file{test12.avi} will contain first four streams from
the input file in reverse order.

@end itemize
@c man end EXAMPLES

@include eval.texi
@include encoders.texi
@include demuxers.texi
@include muxers.texi
@include indevs.texi
@include outdevs.texi
@include protocols.texi
@include bitstream_filters.texi
@include filters.texi
@include metadata.texi

@ignore

@setfilename avconv
@settitle avconv video converter

@c man begin SEEALSO
avplay(1), avprobe(1), avserver(1) and the Libav HTML documentation
@c man end

@c man begin AUTHORS
The Libav developers
@c man end

@end ignore

@bye